As a method of visualizing the surroundings of a vehicle that belongs to currently known apparatuses, there is a top view system based on multichannel image synthesis. This is used to synthesize images of the surroundings of a vehicle that represent blind zones that are present out of the field of view of a driver. The top view output apparatus outputs a plurality of images obtained via cameras installed in front of, in back of, on the left of and on the right of a vehicle in the form of a single continuous image. That is, it generates a 2D plane image in the form of a top view that seems to be viewed from the upper end of the vehicle.
When a top view output apparatus using a plurality of cameras is applied to a bird's eye image, attention should be paid to installation so that the cameras basically use fisheye lenses having a field of view of about 180 degrees and thus common areas are ensured between neighboring cameras.
Conventional top view output apparatuses model ground plane information around a vehicle by combining algorithms, including lens distortion correction, pattern extraction, and the conversion of a point of view via homography, after images have been obtained from cameras in a tolerance correction process. These top view output apparatuses are systems that intuitively visualize information around a vehicle and continuously represent ground plane information, such as parking lines, around the vehicle over an omnidirectional range of 360 degrees around the vehicle.
However, the top view output apparatuses have several realistic limitations. First, the top view output apparatuses cannot guarantee the continuity of a ground object, other than a ground plane, because they do not take into consideration the continuity of a ground plane object. Furthermore, when images are synthesized, the distortion of a ground object is considerably increased because the top view output apparatus considers the ground object to be a ground plane object. As a result, a synthetic image displayed by the top view output apparatus appears to be a planar image that is somewhat different from a real image of the surroundings of a vehicle. Accordingly, the top view output apparatuses have low visibility with respect to a ground object.
Second, most of the currently developed top view output apparatuses represent a region of interest with a specific boundary set around a vehicle. The currently developed top view output apparatuses generally represent only an adjacent area, narrower than an area whose boundary is 2 m away from the front, back, and left and right sides of the vehicle, around a vehicle. If they represent an area wider than an area whose boundary is more than 2 m away from a vehicle, the degradation of image quality is serious and distortion is high, and thus it is difficult to apply them to practical use. In particular, the problem of the degradation of image quality occurs because information about a remote area in input images is significantly insufficient compared to that of a remote plane image whose representation is desired. Furthermore, if upon reverse parking, it is considered that a series of parking steps that are performed by a driver include the determination of the stopped and moving states of objects around a vehicle and the relative distances to the objects, the visual area actually supported by the top view output apparatuses may be viewed as too narrow to detect/determine the above-described elements. Accordingly, the top view output apparatuses have narrow visual areas.
Third, the distortion of a ground object, other than a plane, can be easily found in a synthetic image because the top view output apparatuses make information about the surroundings of a vehicle planar. This phenomenon caused by distortion in an algorithm is indispensable in terms of the characteristics of its principle. In particular, the phenomenon of the distortion of a ground object may become a critical problem when a driver interprets a synthetic image displayed via such an output apparatus. For example, if the synthesis device outputs a distorted image of an infant near a vehicle and a driver does not recognize an infant and drives the vehicle without taking any measures, fatal consequences may result. Accordingly, the top view output apparatuses perform impractical visualization over a wide range.